In situ recombination junction between p-Si and TiO2 enables high-efficiency monolithic perovskite/Si tandem cells
Heping Shen a, Stefan Omelchenko b, Daniel Jacobs a, Sisir Yalamanchili b, Nathan Lewis c, Kylie Catchpole a
a Research School of Engineering, The Australian National University
b Joint Center for Artificial Photosynthesis, California Institute of Technology
c Division of Chemistry and Chemical Engineering, California Institute of Technology
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Oral, Heping Shen, presentation 035
Publication date: 11th February 2019

The price of silicon (Si) photovoltaic modules has dropped nearly exponentially over the past few decades, with balance of systems costs now accounting for majority (~70%) of a fully installed solar electricity system. Hence further reductions in the cost of Si photovoltaics can be most readily met by increasing the module efficiency and thereby reducing the area-related balance of systems costs. The current laboratory record of power conversion efficiency for single-junction Si solar cells is 26.6%, leaving marginal improvement considering the theoretical limit of ~29%. Combining multiple junctions in a single device is one of the most practical and well demonstrated approaches to overcome this limitation. Efficiencies above the single-junction Shockley-Queisser limit of 32% under 1-sun illumination have been obtained by combining III-V top cells with a Si bottom cell; however, a number of obstacles impede the commercial viability of this pairing, including the high materials and fabrication costs of III-V semiconductors. Because of their large bandgap tunability, low materials cost, simple processing requirements and outstanding optoelectronic properties, inorganic-organic metal-halide perovskite materials are attractive candidates for the top cell in a tandem structure with Si.

In our work, we describe a two-terminal perovskite/Si tandem design that increases the Si cell’s output in the simplest possible manner: by placing a perovskite cell directly on top of the Si bottom cell. The advantageous omission of a conventional interlayer eliminates both optical losses and processing steps and is enabled by the low contact resistivity attainable between n-type TiO2 and Si, established here using atomic layer deposition. We fabricated proof-of-concept perovskite/Si tandems on both homojunction and passivating contact heterojunction Si cells to demonstrate the broad applicability of the interlayer-free concept. Stabilized efficiencies of 22.9 and 24.1% were obtained for the homojunction and passivating contact heterojunction tandems, respectively, which could be readily improved by reducing optical losses elsewhere in the device. We also proposed mechanism to understand how the devices operate efficiently by studying the TiO2/Si interface in both experiments and numerical simulations. This work highlights the potential of emerging perovskite photovoltaics to enable low-cost, high-efficiency tandem devices through straightforward integration with commercially relevant Si solar cells.

© Fundació Scito
We use our own and third party cookies for analysing and measuring usage of our website to improve our services. If you continue browsing, we consider accepting its use. You can check our Cookies Policy in which you will also find how to configure your web browser for the use of cookies. More info