Single-junction photovoltaics have a theoretical efficiency limit of 33.7%, with over 50% energy losses in thermalization and in-band transparency. Prior engineering at system levels has been developed to reduce these losses and break the Shockley-Queisser (SQ) limit; many require high-standard manufacturing but deliver mild efficiency enhancement. A breakthrough can be found from the materials perspective. Halide perovskites with various physical merits may provide the platform to overcome both thermalization and in-band transparency losses and thus elevate efficiency by two factors. For example, long-lived hot carriers in perovskite could boost the photovoltage to exceed its band gap or to execute a multi-exciton generation process to double the photocurrent. A delicately designed quantum structure could overcome the in-band losses by mechanisms such as intermediate band, multiple quantum well cascade, and photoferroic effect. Here, we discuss the opportunity, feasibility, and challenges of overcoming the SQ limit by designing upon a perovskite platform.
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