Hot‐carrier solar cells and improved types using wide‐bandgap energy‐selective contacts

Abstract

AbstractI evaluated conversion efficiency of hot‐carrier solar cells (HC‐SCs) of the original type and two improved types: an HC‐SC with intraband transition (HC‐SC+intra) and an intermediate‐band‐assisted HC‐SC (IB‐HC‐SC) that utilize sub‐bandgap photons. For this purpose, three realistic points of great importance were involved in the newly constructed detailed‐balance model: Shockley–Read–Hall (SRH) recombination of photogenerated carriers, characteristics of the energy‐selective contacts (ESCs), and solar spectrum variation. I have revealed that the HC‐SC+intra and IB‐HC‐SC can potentially yield annual electricity production comparable to those of triple‐junction and quad‐junction solar cells (3J‐ and 4J‐SCs) when sub‐bandgap photons are almost perfectly absorbed. The ESCs consisting of wide‐bandgap layers extract the photogenerated carriers more rapidly owing to their larger conductance and consequently yield higher conversion efficiency than the ESCs using resonant tunneling diodes composed of quantum dots and quantum wells. This, in turn, enables the use of an absorber with a short SRH recombination time of the carriers. In other words, the efficiency is less sensitive to SRH recombination than those of the 3J‐ and 4J‐SCs. In particular, for the IB‐HC‐SC, the requisite of the SRH recombination time is 1 ns, and that of the thermalization time is 0.1 ns; the latter is an order of magnitude shorter than the previous requisite. These HC‐SCs are more robust against the solar spectrum variation because they are free from the current‐matching problem unlike the 3J‐ and 4J‐SCs, which also contributes to the large annual electricity production.