Thermoelectric field effects in low-dimensional structure solar cells

Abstract

Taking into account the temperature gradients in solar cells, it is shown that their efficiency can be increased beyond the Shockley-Queisser-limit [1]. The driving force for this gain is the temperature gradient between this region and its surroundings. A quantitative theory is given. Though the effect is found to be weak in conventional solar cells, it is argued that it can be substantially increased by proper choice of materials and design of the device. In particular, it is shown that the insertion of a quantum well can enhance the efficiency beyond the one of a single gap cell, due to the presence of temperature jumps at the heterojunctions.

Quantitative experimental assessment of hot carrier-enhanced solar cells at room temperature

“…Layer composition and thicknesses are given in Figure 1. The wafer structure has been optimized from the results of our previous work [6] which optically showed the evidence of hot carrier effects in a quantum well/barriers absorber. The multilayer wafer contains an intrinsic InGaAsP-based quantum well/barriers region, playing the role of absorber which generates hot charge carriers.…”

“…Indeed thermoelectric devices convert heat gradients into electrical energy and photovoltaic devices convert light flux 1 into electrical energy. Hight lattice thermal conductivity of usual semiconductors would generally prevent a direct use of thermoelectric effect [6]. To fight lattice conductivity one option is to keep the lattice isothermal while only the photogenerated carriers can become hot [4,8].…”

Miniaturized TEG with thermal generation of free carriers

“…Hence, this device acts as a thermoelectric power source. A similar effect was proposed for enhancing the efficiency in solar cells due to thermal gradients 10. In order to substitute a metallic contact, the reverse biased pn‐junction at the hot side has to be able to transport the same electric current as the met al Normally, pn‐junctions are designed to block reverse currents, but deriving the thermal generation of free carriers within the pn‐junction using the Shockley–Reed–Hall (SRH) model 9 shows that also the opposite effect, a very high conductivity, can be achieved.…”

Optoelectronic characterization of carrier extraction in a hot carrier photovoltaic cell structure

“…The hot carrier solar cell is a heat engine; supplementing or supplanting the photovoltaic action of a traditional solar cell with a thermally driven current, analogous to a thermoelectric device [1]. With this additional channel for energy extraction it is, in principle, possible for these cells to achieve efficiencies up to 85% [2], since the thermalization loss of high energy carriers is mitigated through their contribution to the heat current.…”