A pinboard by
Hansong Xue

I am a Doctor of Engineering candidate at National Univerisity of Singapore research in Solar Cells


Mathematical Modelling and Analysis of Perovskite Solar Cells

A perovskite solar cell is a type of solar cell which consists of perovskite structured compound as its light harvesting active layer. The most commonly used perovskite compound is a hybrid organic-inorganic lead. This type of material and its fabrication process are both at a much lower cost than the currently commercialized silicon solar cells in the market. In addition, it can absorb the complete visible solar spectrum around 500nm due to its high absorption coefficient. Therefore, it is possible to create low cost, high efficiency, thin, lightweight and flexible perovskite solar cells modules for commercialization.

Recently, the pursuit of organic-inorganic perovskite solar cells has been significantly advanced because of the promising high-efficiency potential of the perovskite materials. Based on the structure of dye sensitized solar cells, Miyasaka et al. firstly incorporated a perovskite material into a solar cell, thereby achieving 3.8% conversion efficiency. Afterward, many groups contributed to the development of perovskite solar cells and as a result, its efficiency increased quickly to 22.1% in this year. In addition to the advancement in experimental studies, the modelling and numerical simulation of perovskite solar cells also grew recently, as it can aid in elucidating the device physics, unveiling its intrinsic material properties and predicting the device performance.

Our group develops in-depth mathematical device model for perovskite solar cells. This mathematical model is able to capture the physical phenomena of all four standard types of perovskite solar cells, namely mesoporous configuration, extreme thin absorber configuration, planar n-i-p configuration and planar p-i-n configuration. After calibrating and validating the resulting model with in-house fabricated meso-structured solar cells, we perform a subsequent loss analysis for meso-structured perovskite solar cells. This can provide insights for further improving the solar cell device architecture of meso-structured perovskite solar cells and their efficiency. Our implemented device model is generic enough to compare the different physical phenomena occurring in perovskite solar cells processed in a meso-structured configuration compared to those processed in a planar configuration.


High-efficiency two-dimensional Ruddlesden-Popper perovskite solar cells.

Abstract: Three-dimensional organic-inorganic perovskites have emerged as one of the most promising thin-film solar cell materials owing to their remarkable photophysical properties, which have led to power conversion efficiencies exceeding 20 per cent, with the prospect of further improvements towards the Shockley-Queisser limit for a single-junction solar cell (33.5 per cent). Besides efficiency, another critical factor for photovoltaics and other optoelectronic applications is environmental stability and photostability under operating conditions. In contrast to their three-dimensional counterparts, Ruddlesden-Popper phases-layered two-dimensional perovskite films-have shown promising stability, but poor efficiency at only 4.73 per cent. This relatively poor efficiency is attributed to the inhibition of out-of-plane charge transport by the organic cations, which act like insulating spacing layers between the conducting inorganic slabs. Here we overcome this issue in layered perovskites by producing thin films of near-single-crystalline quality, in which the crystallographic planes of the inorganic perovskite component have a strongly preferential out-of-plane alignment with respect to the contacts in planar solar cells to facilitate efficient charge transport. We report a photovoltaic efficiency of 12.52 per cent with no hysteresis, and the devices exhibit greatly improved stability in comparison to their three-dimensional counterparts when subjected to light, humidity and heat stress tests. Unencapsulated two-dimensional perovskite devices retain over 60 per cent of their efficiency for over 2,250 hours under constant, standard (AM1.5G) illumination, and exhibit greater tolerance to 65 per cent relative humidity than do three-dimensional equivalents. When the devices are encapsulated, the layered devices do not show any degradation under constant AM1.5G illumination or humidity. We anticipate that these results will lead to the growth of single-crystalline, solution-processed, layered, hybrid, perovskite thin films, which are essential for high-performance opto-electronic devices with technologically relevant long-term stability.

Pub.: 08 Jul '16, Pinned: 28 Jul '17