Understanding and Weakening Photon Recycling in Solar Cells to Approach the Radiative Limit.

Photon recycling plays an important role in the light outcoupling of state-of-the-art solar cells and is considered a necessary condition to achieve the radiative limit of open-circuit voltage (V OC ) and efficiency. However, due to the impact of photon recycling on bulk and surface radiation of solar cells being overlooked, experimental demonstrations on the accuracy of existing photon recycling models are scarce and some contrary theoretical results also emerge. Here, the relationship between photon recycling and radiation processes, as well as the corresponding V OC losses of solar cells based on the principle of detailed balance is clarified. It is shown that weakening photon recycling is more effective to boost the device performance than enhancing it, promoting the theoretical efficiencies of solar cells, such as perovskite, Si, and GaAs, to 98.5%, 94.9%, and almost 100% of their radiative limit, respectively. Moreover, weakening photon recycling also helps to maintain higher efficiency when the internal radiative efficiency decreases, which benefits higher device stability. This work provides an in-depth understanding of the role of photon recycling in solar cells and helps to push efficiency to a new limit.