Recently, Professor Zhang Yi, from the College of Electronic Information and Optical Engineering, Nankai University, has made important progress in the research and development of CZTSSe thin-film batteries. In collaboration with Professor Liu Shengzhong of Shaanxi Normal University and Professor Yu Wei of Hebei University, he introduced an ultra-thin layer of Al2O3 on the precursor film by ALD, which successfully controlled the distribution behavior of Ag during high-temperature annealing, and the surface contact potential difference increased from -230 mV of undoped Ag to +111 mV (Figure 1). Moreover, the valence band top position of the absorption layer gradually decreases from 0.63 eV below the fermi level to 0.12 eV from the surface to the interior of the absorption layer, which proves that when Ag is enriched on the surface of the absorption layer, not only the polarity of potential is reversed on the surface of the film, but also the conductivity type is reversed from the perspective of energy band.

Figure 1. AFM diagrams a and d), KPFM potential diagrams b and e) and surface contact potential difference distributions c and f). a-c) CZTSSe samples without Ag doping; d-f) CZTSSe samples with Ag doping.

This novel Ag doping strategy reduces the recombination of the interface and the absorption layer, where the realized absorption layer modification and efficient energy band engineering bring new light to the future of CZTSSe solar batteries. The related results have been published in Advanced Materials (DOI: 10.1002/ADMA. 202104330) with the title of N-type Surface Design for p-type CZTSSe Thin Film to Attain High Efficiency. Professor Zhang Yi and Professor Liu Shengzhong are co-corresponding authors and Nankai University is the first author unit. This work has been funded by the key projects of the National Key Research and Development Plan and the key projects of the National Natural Science Foundation of China.

Link to the paper: https://onlinelibrary.wiley.com/doi/10.1002/adma.202104330

(Reported by Zhao Ying, Liu Bo, Zhang Yi and Zhu Bochen, edited and translated by Nankai News Team.)