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arXiv · 2505.03253

Sub-micron Cu(In,Ga)Se2 solar cell with efficiency of 18.2% enabled by a hole transport layer

Taowen Wang·Longfei Song·Saeed Bayat·Michele Melchiorre·Nathalie Valle·Adrian-Marie Philippe·Emmanuel Defay·Sebastjan Glinsek·Susanne Siebentritt
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Abstract

Reducing the thickness of Cu(In,Ga)Se2 solar cells is a key objective in order to reduce production cost and to improve sustainability. The major challenge for sub-micron Cu(In,Ga)Se2 cells is the recombination at the backside. In standard Cu(In,Ga)Se2 backside recombination is suppressed by a bandgap gradient, acting as a back surface field. This gradient is difficult to maintain in sub-micron thick absorbers. In this study, a hole transport layer passivates the back contact and enables efficient sub-micron Cu(In,Ga)Se2 solar cells without the need of a Ga gradient. The backside passivation by the hole transport layer is as effective as an optimized Ga gradient, resulting in a significant increase in open-circuit voltage by 80 mV in comparison to the reference sample without passivation. Moreover, the hole transport layer exhibits good transport properties, leading to a fill factor as high as 77%. Photoluminescence quantum yield of 0.15% and solar cell efficiency above 18% are demonstrated in sub-micron Cu(In,Ga)Se2 absorbers.

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Taowen Wang, Longfei Song, Saeed Bayat, Michele Melchiorre, Nathalie Valle, Adrian-Marie Philippe, Emmanuel Defay, Sebastjan Glinsek, Susanne Siebentritt. 2025-05-06. Sub-micron Cu(In,Ga)Se2 solar cell with efficiency of 18.2% enabled by a hole transport layer. https://doi.org/10.1039/d5el00049a

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