Polymer:nonfullerene solar cells with an inverted-type device structure were fabricated by employing the bulk heterojunction (BHJ) active layers, which are composed of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] (PBDB-T) and 3,9-bis(6-methyl-2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IT-M). The BHJ layers were formed on a pre-patterned indium-tin oxide (ITO)-coated glass substrate by spin-coating using the blend solutions of PBDB-T and IT-M. The solar cell performances were investigated with respect to the cell position on the ITO-glass substrates. In addition, the short-term shelf lifetime of solar cells was tested by storing the PBDB-T:IT-M solar cells in a glovebox filled with inert gas. The results showed that the performance of solar cells was relatively higher for the cells close to the center of substrates, which was maintained even after storage for 24 h. In particular, the PCE of PBDB-T:IT-M solar cells was marginally decreased after storage for 24 h owing to the slightly reduced fill factor, even though the open circuit voltage was unchanged after 24 h.

In this study, we investigate organic-inorganic hybrid solar cells with a very simple three-layer structure (Al/n-Si/PEDOT:PSS). The performance of hybrid solar cells is optimized by controlling the sheet resistance and optical transmittance of the PEDOT:PSS layers. As the thickness of the PEDOT:PSS layer decreases, the optical absorption of the n-Si increases, which greatly improves the short-circuit current density ($J_{SC}$) of devices, but the increase in sheet resistance leads to a decrease in the open-circuit voltage ($V_{OC}$) and the fill factor (FF). The solar cell with the 180-nm thick PEDOT:PSS layer shows a highest efficiency of 8.45% ($V_{OC}$: 0.435 V, $J_{SC}$: $33.7mA/cm^2$, FF: 57.5%). Considering these results, it is expected that the optimizing process for the sheet resistance and transmittance of the PEDOT:PSS layer is essential for producing high-efficiency organic-inorganic hybrid solar cells and will serve as an important basis for achieving low-cost, high-efficiency solar cells.

As a demand of higher power photovoltaic modules, shingled, multi-busbar, half-cell, and bifacial techniques are developed. Multi-busbar module has advantage for large amount of light havesting. And, half-cell is high power module for reducing resistive losses and higher shade tolerance. Recently, researches on multi-busbar is focused on reliability according to adhesion and intermetallic compound between Sn-Pb solder and Ag electrode. And half-cell module is researched to comparing with full-sized cell module for structure difference. In this study, we investigated the factors affecting to efficiency and adhesion of multi-wires half-cell module according to wire thickness, solder thickness, and flux. The results of solar simulator and peel test was that peel strength and efficiency of soldered cell is not related. But samples with flux including high solid material showed high efficiency. The results of FE-SEM and EDX line scan on cross-section between wire and Ag electrode for different flux showed thickness of solder joint between wire and Ag electrode is increasing through solid material increasing. Flux including high solid material would affect to solder behavior on Ag electrode. Higher solid material occurred lower growth of IMC layer because solder permeate to sider of wire ribbon than Ag electrode. And it increased fill factor for high efficiency. In soldering process, amount of solid material in flux and solder thickness are the factor related with characteristic of soldered photovoltaic cell.

Solar energy is one of the renewable energy sources. It can respond to expanding energy demand. A solar cell module is designed to have a durability that can be developed over a long period of 25 years to be installed outdoors and perform like a stable power supply. We need Standard Test Condition (STC)-based power output data before and after testing to measure the power output of existing modules. The modules are shown to reduce power output by comparing data before and after outdoor experiments regardless of whether they are indoor or outdoor. It is easy to compare the power output quantities through the module simulator in the indoor. However, it takes a lot of testing time and costs to compare the power output on outdoor in the case of a high number of modules and distance from the module simulator. It can save time and costs if we can check the power output using the data in outdoor. We have used the long-term outdoor test to find the elements out that corresponds to the reductions in power output quantities. We have conducted research that matched the actual and the tests.

Silicon heterojunction solar cells (SHJ) have dominated the photovoltaic market up till now but their conversion performance is practically limited to around 26% compared with the theoretical efficiency limit of 29.4%. A silicon based multi-junction devices are expected to overcome this limitation. In this report, we briefly review the state-of-art characteristic of wide-gap materials which has played a role as top sub-cells in silicon based multi-junction solar cells. In addition, we indicate significantly practical challenges and key issues of these multi-junction combination. Finally, we focus to some characteristics of III-V/c-Si tandem configuration which are reaching highly record performance in multi-junction silicon solar cells.