• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.395-396
• /
• 2011

본 논문에서는 30% 내외의 평균반사율을 가지는 다결정 실리콘 태양전지의 입사광 손실을 최소화하여 광전변환효율 극대화를 구현하기 위해서 SF6/O2 혼합가스를 이용한 RIE 표면 texturing 공정을 수행하였다. 현재 다결정 실리콘 태양전지는 다양한 방향의 grain을 가지기 때문에 단결정 실리콘에 적용되는 습식 식각 방식이 다결정 실리콘 표면 texturing에 적절하지 않은 것으로 알려져 있다. 이를 개선하기 위해서 이방성 식각 특성을 가지는 다양한 texturing 방법이 시도되고 있다. 대표적으로 기계적인 방식의 V-grooving, 레이저 grooving, 플라즈마 건식식각을 이용한 texturing 및 산 용액을 이용한 texturing 등의 연구가 보고되고 있다. 그 중에서 플라즈마 건식식각 방식의 하나인 RIE를 이용한 표면 texturing 공정이 간단한 공정과 산업계 응용의 용이성 때문에 활발히 연구되어 왔다. 특히 Sandia group과 일본 Kyocera사의 연구 결과에서는 그 가능성을 입증하고 있다. 본 연구에서는 공정의 단순화와 안전한 공정을 위해서 SF6/O2 혼합 가스를 이용하여 마스크 패턴 공정없이 RIE texturing 공정을 수행하였으며, RIE-textured 다결정 실리콘에 대해서 태양전지를 제작하여 표면 texturing이 광전변환효율에 미치는 영향에 대해서 분석하였다. 그 결과 SF6/O2 혼합 가스를 이용한 RIE texturing은 다결정 실리콘 표면에 주로 needle 구조를 형성하는 것을 확인하였다. 각 texturing 조건별 반사율의 차이는 needle 구조의 조밀도와 관련되는 것을 알 수 있었으며, 동일 공정 parameter 상에서 식각 시간 1, 2, 3, 4, 5분 기준 시간에 따른 표면 구조 분석 결과 seed 가 형성되고 그에 따라서 needle 형태로 식각되는 과정을 관찰하였다. 반사율은 분당 약 4%씩 낮아져 5분 식각 후 14.45% 까지 낮아졌으며, 표면 구조에서 폭은 약 30 nm로 모두 일정하며, 길이가 약 20, 30, 50, 80, 100 nm으로 증가되었다. 이 결과로 보아 seed로부터 needle 구조가 심화되어가는 것을 알 수 있었다. 시간에 따른 RIE texturing 후 제작된 태양전지는 효율이 1분 식각 기준 15.92%에서 약 0.35% 씩 낮아져 5분 식각 후 14.4%로 낮아졌다. Voc 는 texturing 시간에 관계없이 일정하며 Isc가 점점 감소되는 것으로 확인되었다. EQE 결과도 이와 동일하게 RIE texturing 시간이 길어질수록 전체 파장 범위에서 일정하게 낮아지는 것이 관찰되었다. Electroluminescence(EL) 이미지 결과 texturing 시간이 길어진 태양전지일수록 점점 어두운 이미지가 나타나 5분 식각의 경우 가장 어두운 결과를 나타내었다. 이런 결과는 한 가지 이유보다는 복합적인 문제로 예상되는데 궁극적으로는 RIE 공정 후 표면에 쌓인 charged particle들이 trap 준위를 형성하여 효율 및 공정상에 영향을 미친 것으로 보이며, 특히 잔류 O기가 불균일한 산화막을 형성하는 것으로 예상된다. 또한 EL 분석 결과를 볼 때 RIE texturing 공정이 길어질수록 불안정한 pn-junction을 형성하는 것을 확인하였으며, emitter 층 형성 후 PSG (phosphorous silica glass) 공정에서 needle의 상부 구조가 무너지면서 면저항이 증가된 결과로 분석된다. PSG 제거 후 측정된 면저항의 경우 3분 texturing 샘플부터 면저항이 약 4${\Omega}/sq$ 정도 증가됨을 확인하였다.

• Journal of the Microelectronics and Packaging Society
• /
• v.27 no.3
• /
• pp.69-72
• /
• 2020

In this study, the inverted structured electroluminescence (EL) devices were fabricated with double electron transport layers (ETLs). The conduction band minimum (CBM) of TiO₂ NPs is lower than SnO₂ NPs. Therefore, it is expected that inserting TiO₂ NPs between the SnO₂ layer and the emission layer (EML) will reduce the energy barrier and transport electrons smoothly. The quantum dot light emitting diodes (QLEDs) with double ETLs showed the enhanced emission characteristics than those with only SnO₂ layer.

• Journal of Information Display
• /
• v.3 no.1
• /
• pp.6-10
• /
• 2002

We have synthesized a new green Ir(III) complex fac-tris-(3-methyl-2-phenyl pyridine)iridium(III) $Ir(mpp)_3$ and fabricated phosphorescent polymer light-emitting device using it as a triplet emissive dopant in PVK. $Ir(mpp)_3$ showed absorption centered at 388 nm corresponding to the $^1MLCT$ transition as .evidenced by its extinction coefficient of the order of $10^3{\cdot}$ From the PL and EL spectra of the $Ir(mpp)_3$ doped PVK film, the emission maximum was observed at 523 nm, due to the radiative decay from the $^3MLCT$ state to the ground state, confirming a complete energy transfer from PVK to $Ir(mpp)_3$. The methyl substitution has probably caused a red shift in the absorption and emission spectrum compared to $Ir(mpp)_3$. The device consisting of a 2 % doped PVK furnished 4.5 % external quantum efficiency at 72 $cd/m^2$ (current density of 0.45 $mA/cm^2$ and drive voltage of 13.9 V) and a peak luminance of 25,000 $cd/m^2$ at 23.4 V (494 $mA/cm^2$). This work demonstrates the impact of the presence of a methyl substituent at the 3-position of the pyridyl ring of 2-phenylpyridine on the photophysical and electroluminescence properties.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.382-382
• /
• 2011

보다 저렴한 다결정 실리콘 웨이퍼를 사용한 다결정 실리콘 태양전지의 발전효율개선을 위해서는 태양광스펙트럼의 표면 흡수기구를 최적화하고, 전자-정공쌍의 생성극대화 및 재결합 기구 제어를 통한 전하운바자들의 안정적인 분리와 전극으로의 효율적인 수집이 필수적인다. 현재 양질의 다결정 실리콘 웨이퍼에 기반한 다결정 실리콘 태양전지 양산공정에서 16~17% 발전효율이 이루어지고 있으며 18% 이상의 발전효율을 얻기 위해서는 보다 더 우수한 품질의 다결정 실리콘 웨이퍼가 요구된다. 본 연구에서는 15.5~16.5% 대역의 평균 발전효율을 갖는 15.6 cm${\times}$15.6 cm 크기 고효율 다결정 실리콘 태양전지 전면의 전자발광(EL : electroluminescence)데이터로부터 효율기여도가 높은 위치와 상대적으로 기여도가 낮은 위치들을 선정하여 380~1050nm 파장대역의 광선속에 대해 국부적인 외부양자효율(EQE : external quantum efficiency)을 측정하고 투과전자현미경(TEM : tunneling electron microscope) 등을 활용하여 결정방향 등에 기인하는 양자효율 악화기구를 분석하였다. 결론적으로 15%대의 상대적으로 낮은 발전효율을 보이는 태양전지들은 300~600 nm 단파장 영역에서 양자효율이 상대적으로 낮은 저급한 결정성의 웨이퍼에 기인하고 16.5%이상의 높은 발전효율을 갖는 태양전지들은 단파장영역에서 높은 양자효율을 갖는 영역이 수광면적의 80~90%를 차지하는 것으로 밝혀졌다. 이와 더불어 15%대의 발전효율을 갖는 태양전지에서는 600~1100 nm 파장대역에서 상대적으로 악화된 양자효율을 갖는 저급한 결정성 영역이 30~40%를 차지하였으나 16.5%대역의 고효율 태양전지에서는 저급한 결정성 영역이 5~10%를 차지하여 대조를 보였다. 따라서 18%이상의 높은 발전효율을 갖는 다결정 실리콘 태양전지의 양산을 위해서는 양자효율이 우수한 양품의 웨이퍼를 기반으로 표면 texturing을 통해 평균 태양광 흡수율을 90%이상으로 개선하고, 보다 미세한 프론트 전극패턴을 통해 수광면적을 개선하고 선택적인 에미티공정 기술 등을 적용할 필요가 있음을 제안하고자 한다.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.10
• /
• pp.2955-2960
• /
• 2010

Spiro-type orange phosphorescent host materials, 9-diphenylphosphine oxide-spiro[fluorene-7,9'-benzofluorene] (OPH-1P) and 5-diphenylphosphine oxide-spiro[fluorene-7,9'-benzofluorene] (OPH-2P) were successfully prepared by a lithiation reaction followed by a phosphination reaction with diphenylphosphinic chloride. The EL characteristics of OPH-1P and OPH-2P as orange host materials doped with iridium(III) bis(2-phenylquinoline)acetylacetonate ($Ir(pq)_2acac$) were evaluated. The electroluminescence spectra of the ITO (150 nm)/DNTPD (60 nm)/NPB (30 nm)/OPH-1P or OPH-2P: $Ir(pq)_2acac$ (30 nm)/BCP (5 nm)/$Alq_3$ (20 nm)/LiF (1 nm)/Al (200 nm) devices show a narrow emission band with a full width at half maximum of 75 nm and $\lambda_{max}$ = 596 nm. The device obtained from OPH-1P doped with 3% $Ir(pq)_2acac$ showed an orange color purity of (0.580, 0.385) and an efficiency of (14 cd/A at 7.0 V). The ability of the OPH-P series to combine a high triple energy with a low operating voltage is attributed to the inductive effect of the P=O moieties and subsequent energy lowering of the LUMO, resulting in the enhancement of both the electron injection and transport in the device. The overall result is a device with an EQE > 8% at high brightness, but operating voltage of less than 6.4 V, as compared to the literature voltages of ~10 V.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08a
• /
• pp.667-670
• /
• 2007

A new series of highly bright and efficient poly(pphenylenevinylene) s (PPV)s based on polyhedral oligomeric silsesquioxanes (POSSs) was synthesized via the Gilch polymerization method. The three POSScontaining PPVs are as follows: POSS05- PPV(containing 5 mol % POSS-appended PPV units), POSS25-PPV(containing 25 mol % POSS-appended PPV units), and POSS100-PPV(containing 100 mol % POSS-appended PPV units; this is the first ${\pi}-conjugated$ polymer composed of 100 mol % POSSsappended repeating units). The POSS-containing PPVs exhibit higher glass transition temperatures $(64-77^{\circ}C)$ than that of MEH-PPV $(58^{\circ}C)$, indicating that electroluminescence (EL) devices fabricated with these polymers should have good thermal stabilities. Light-emitting diodes (LEDs) with the configuration of ITO/PEDOT:PSS/polymer/Ca/Al were fabricated using the novel POSS-containing PPVs. Surprisingly, the luminescence efficiency (0.48 cd/A at $10540\;cd/m^2$) of the binary blend consisting 5 wt % of POSS25-PPV and 95 wt % of MEH-PPV was found to be enhanced by a factor of 6.4 with a maximum brightness of $11010cd/m^2$ (at 14.3 V).

• Proceedings of the KIEE Conference
• /
• 2004.11a
• /
• pp.215-219
• /
• 2004

Metal-chelate derivatives have been investigated intensively as an emitting layer and recognize to have excellent electroluminescence(EL) properties. We synthesized new luminescent material, 1,4-dihydoxy-5,8-naphtaquinone $Aiq_3$ complex($Al_2Nq_4$) and investigated the electrical optical properties. OLED has potential candidates for information display with merits of thickness, low power and high efficiency. Although the OLED show a lot of advantages for information display, it has the limit of inorganic(metal)/ organic interface. In this study, the two methods are used to study the interface of metal/organic in OLED. First, we treated $O_2$ plasma on an ITO thin film by using RIE system, and analyzed the ingredient of ITO thin film according to change of the processing conditions. We used the RDS and the XPS for the ingredient analysis of the surface and bulk. We measured electrical resistivity using Four-Point-Probe and calculated sheet resistance, and ITO surface roughness was measured by using AFM. We fabricated OLED using substrate that was treated optimum ITO surface. Second, we used the buffer layer of CuPc to improve the characteristics of the interface and the hole injection in OLED. The result of the study for electrical and optical properties by using I V L T System(Flat Panel Display Analysis System), we confirmed that the electrical properties and the luminance properties were improved.

• Journal of the Korean Chemical Society
• /
• v.54 no.3
• /
• pp.291-294
• /
• 2010

In this study, we demonstrated high-efficiency blue organic light-emitting diodes (OLEDs) employing BCzVBi as a blue fluorescent dye doped into blue host material, DPVBi with various concentration. The optimized blue OLED device having high-efficiency was constructed with structure of NPB (500 ${\AA}$) / DPVBi:BCzVBi-6% (150 ${\AA}$)/$Alq_3$(300 ${\AA}$) / Liq (20 ${\AA}$) / Al (1000 ${\AA}$). The maximum luminescence of blue OLED was 13200 cd/$m^2$ at 13.8 V and current density and maximum efficiency were 26.4 mA/$cm^2$ at 1000 cd/$m^2$ and 4.24 cd/A at 3.9 V, respectively. Luminous efficiency shows two times higher than comparing with non-doped BCzVBi blue OLED whereas $CIE_{x,y}$ coordinate was similar with bare DPVBi blue OLED such as (0.16, 0.19). Electroluminescence of BCzVBi-6% doped blue OLED has two major peaks at 445 nm and 470 nm whereas pure DPVBi's blue peak appears at 456 nm and it is happened through endothermic Forster energy transfer by molecule's vibration between LUMO of DPVBi as host material and LUMO of BCzVBi as dopant in device.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.153-153
• /
• 2010

Recently, to develop GaN-based light-emitting diodes (LEDs) with better performances, various approaches have been suggested by many research groups. In particular, using the patterned sapphire substrate technique has shown the improvement in both internal quantum efficiency and light extraction properties of GaN-based LEDs. In this paper, we discuss the influences of the direction of the hexagonal-structure arrays of lens-shaped patterns (HSAPs) formed on sapphire substrates on the crystal, optical, and electrical properties of InGaN/GaN multi-quantum-well (MQW) LEDs. The basic direction of the HSAPs is normal (HSAPN) with respect to the primary flat zone of a c-plane sapphire substrate. Another HSAP tilted by 30o (HSAP30) from the HSAPN structure was used to investigate the effects of the pattern direction. The full width at half maximums (FWHMs) of the double-crystal x-ray diffraction (DCXRD) spectrum for the (0002) and (1-102) planes of the HSAPN are 320.4 and 381.6 arcsecs., respectively, which are relatively narrower compared to those of the HSP30. The photoluminescence intensity for the HSAPN structure was ~1.2 times stronger than that for the HSAP30. From the electroluminescence (EL) measurements, the intensity for both structures are almost similar. In addition, the effects of the area of the individual lens pattern consisting of the hexagonal-structure arrays are discussed using the concept of the planar area fraction (PAF) defined as the following equation; PAF = [1-(patterns area/total unit areas)] For the relatively small PAF region up to 0.494, the influences of the HSAP direction on the LED characteristics were significant. However, the direction effects of the HSAP became small with increasing the PAF.

• Korean Journal of Materials Research
• /
• v.28 no.9
• /
• pp.528-533
• /
• 2018

In recent years, solar cells based on crystalline silicon(c-Si) have accounted for much of the photovoltaic industry. The recent studies have focused on fabricating c-Si solar modules with low cost and improved efficiency. Among many suggested methods, a photovoltaic module with a shingled structure that is connected to a small cut cell in series is a recent strong candidate for low-cost, high efficiency energy harvesting systems. The shingled structure increases the efficiency compared to the module with 6 inch full cells by minimizing optical and electrical losses. In this study, we propoese a new Conductive Paste (CP) to interconnect cells in a shingled module and compare it with the Electrical Conductive Adhesives (ECA) in the conventional module. Since the CP consists of a compound of tin and bismuth, the module is more economical than the module with ECA, which contains silver. Moreover, the melting point of CP is below $150^{\circ}C$, so the cells can be integrated with decreased thermal-mechanical stress. The output of the shingled PV module connected by CP is the same as that of the module with ECA. In addition, electroluminescence (EL) analysis indicates that the introduction of CP does not provoke additional cracks. Furthermore, the CP soldering connects cells without increasing ohmic losses. Thus, this study confirms that interconnection with CP can integrate cells with reduced cost in shingled c-Si PV modules.