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The recent efficiency boosting of Cu(In,Ga)Se2 (CIGS) solar cells is undoubtedly triggered by heavy alkali postdeposition treatments (PDTs). However, the effects are not obvious under monolithically integrated CIGS modules where various current‐shunting sources can deteriorate the device performance. Herein, It is reported that KF PDT can effectively suppress the major shunting sources caused by P1 and P3 laser scribing for monolithic interconnection, reducing the cell‐to‐module (CTM) efficiency gap in CIGS photovoltaics. CIGS with NaF PDT exhibits nearly isotropic and high hole mobilities, causing a large CTM efficiency loss. CIGS with additional KF PDT, on the other hand, reveals much lower in‐plane hole mobility than the out‐of‐plane component, significantly increasing the P1 shunt resistance without exacerbating the photocarrier extraction in the active area. It is suggested that such anisotropic charge transport is due to carrier scattering by low‐conductivity phases at the CIGS grain boundaries. Furthermore, passivation of the front junction by KF PDT raises the tolerance to P3 scribing‐induced damage, increasing the P3 shunt resistance while preserving the junction property unlike the NaF PDT case. The work implies that the recent trend of employing heavy alkali PDTs for a high‐efficiency cell is also crucial for designing a high‐efficiency CIGS module. [ABSTRACT FROM AUTHOR]

Transparent oxide back contact of Cu(In,Ga)Se2 (CIGS) solar cells is crucial for semitransparent or bifacial CIGS photovoltaics. Parasitic GaOx resistive layer formed at the back junction, however, has been the bottleneck for transparent photovoltaic applications. Here, we show that a complementary control of the back junction enabled a high efficiency, semitransparent CIGS module. By employing a thin Ag precursor layer prior to CIGS evaporation, the back‐junction barrier could be eliminated. Atomic probe tomography measurement suggests that an appreciable amount of Ag doping in the GaOx may form hole‐tunneling channels at the back junction. We also found that potassium fluoride (KF) post‐deposition treatment (PDT) increased the back‐junction resistance and the bulk CIGS resistance compared to the case with Na PDT. The KF‐induced increased resistances turned out to be beneficial for suppressing the parasitic shunt current along the P1‐scribing region in our CIGS solar module. Interestingly, J–V rollover caused by the KF‐induced back‐junction barrier completely vanished after see‐through laser scribing of the module. We attribute the barrier‐lowering to a laser‐induced local heating at the back junction. The complementary engineering strategy introduced here would allow functional oxide back contact in CIGS photovoltaic modules for both high efficiency and semi‐transparency. [ABSTRACT FROM AUTHOR]

Harmonizing homogeneity in charge distribution within metal halide perovskite solar cells is essential for maintaining device quality. The adsorption of ions from perovskites onto the electron transport layer leads to the creation of redistributed space‐charge regions (SCR), which facilitate halide segregation and ionic migration, resulting in charge imbalances and diminished extraction capability at the interface. The research examines the intricate interplay between SCRs affecting iodide oxidation and their impact on photovoltaics, uncovering a previously overlooked aspect that the influence of ionic accumulation on electronic charge uniformity. A paradox is identified that electronic charge accumulation at interfaces improves initial open‐circuit voltage, however, compromises stability with a collapsed charge distribution. To address this issue, ion conduction is regulated by utilizing a self‐assembled 2D perovskite resulting from cationic exchange with a low migration barrier at the buried interface, thereby mitigating halide segregation and charge inhomogeneity. This approach exhibits a power conversion efficiency (PCE) of 24.38% with a fill‐factor of 84% and maintains 91.87% of the initial PCE for a duration of 2070 h. [ABSTRACT FROM AUTHOR]

Lead halide perovskites are considered to be most promising photovoltaic materials. Highest efficiency and improved stability of perovskite solar cells have been achieved by using cation and anion mixtures. Experimental information on electronic and ionic charge carriers is key to evaluate device performance, as well as processes of photo‐decomposition and photo‐demixing which are observed in these materials. Here, we measure ionic and electronic transport properties and investigate various cation and anion substitutions with a special eye on their photo‐ionic effect, following our previous study on CH3NH3PbI3, where we found that light enhances not only electronic but also ionic conductivities. We find that this phenomenon is very sensitive to the nature of the halide, while the cationic substitutions are less relevant. Based on the observation that the ionic conductivity enhancement found for iodide perovskites is significantly weakened by bromide substitution, we provide a chemical rationale for the photo‐demixing in mixed halide compositions. [ABSTRACT FROM AUTHOR]

The long stagnation of the photo-conversion efficiency of kesterites below 13% is a source of frustration in the scientific community. In this study, we investigated the effects of sodium on the passivation of grain boundaries and defects in Cu2ZnSnSe4 (CZTSe) grown on a soda-lime glass (SLG) and borosilicate (BS) glass. Because BS glass does not inherently contain sodium, we placed a thin layer of NaF between CZTSe and Mo. The composition of the samples is Cu-poor and Zn-rich. The distribution of sodium and its contributions to phase formation and defects were examined by cross-sectional energy-dispersive X-ray profiling, Raman scattering spectroscopy and imaging, surface potential and photoluminescence. From the experimental results, it can be strongly claimed that sodium ions segregate predominantly near the grain boundaries and reduce CuZn-related defects. These local surface imaging analyses provided the exact locations of the secondary phases. In particular, the photo-assisted scanning probe method enabled us to observe the changes in the optoelectrical properties of the thin films and the carrier behavior within the materials. Further studies with distinct alkali ions and optimal processing conditions will pave a way to improve the performance of kesterite solar cells. [ABSTRACT FROM AUTHOR]