Breaking the Shockley-Queisser (SQ) Limit to Develop a Next Generation of Solar Cell

Abstract: To overcome the well-known Shockley-Queisser (SQ) limit, one novel approach is to utilize the hot carrier generation and collection mechanism, which can achieve more than 67 % power conversion efficiency. A hot carrier is the photogenerated carrier above band gap, due to its extra energy difference between incident photon energy and optical band gap.[i] One signature of the hot carrier photovoltaic (PV) technology is a higher open-circuit voltage (V_OC) than the band gap of solar absorbers.
However, hot carrier PV technology still suffers from the difficulty in collection of the ultra-short time scale hot carrier due to their rapid electron-phonon interaction. In the recent time, hybrid organic-inorganic based perovskite-based structure (e.g., APbX₃, where A = Cs, methylammonium (MA) or formamidinium (FA), X = (Cl, Br, I)) shows their capability in used as hot carrier solar cell due to their prolong carrier lifetime beyond 10s of picosecond or nanosecond, measured by the ultrafast pump-probe and time-resolved photoluminescence.[ii] However, all those characterizations not only investigated the perovskite thin films or solutions, rather than the solar cell working condition (i.e., in-situ), but also limited to the carrier diffusion mechanism, while the photocurrent obey the carrier drift understanding.
Here lies some urgency to characterize the photocurrent within in-situ based perovskite solar cell (PSC) using a novel ultrafast photovoltaic spectroscopy to directly collect the photocurrent, when the solar cell at work.[iii] For the first time, with a sub - 40ps time resolution, we discover a transient V_OC much larger than the band gap of the mixed cation (CsMAFA) perovskite solar cells with >20% efficiency. We further investigate the hot carrier drift transport property, which depends on film thickness and temperature.
Keywords: hot carrier, drift dynamics, charge collection, solar cell


[i] Nozik, A. J. et al., Semiconductor Quantum Dots and Quantum Dot Arrays and Applications of Multiple Exciton Generation to Third-Generation Photovoltaic Solar Cells. Chem Rev 2010, 110, 6873-6890.

[ii] Wang, T. et al., Protecting hot carriers by tuning hybrid perovskite structures with alkali cations. Sci Adv 2020, 6, eabb1336.

[iii] Kobbekaduwa, K.; Liu, E.; Zhao, Q.; Bains, J. S.; Zhang, J.; Shi,Y.; Zheng, H.; Li, D.; Cai, T.; Chen, O.; Rao, A. M.; Beard, M.C.; Luther, J.M.; and Gao, J. Ultrafast Carrier Drift Transport Dynamics in CsPbI₃ Perovskite Nanocrystalline Thin Films. ACS Nano 2023, 17, 13997–14004.