The photo is sourced from NREL
Perovskite solar cells generate electricity by absorbing high-energy photons and passing low-energy photons, which are then absorbed in the semiconductor. Therefore, in developing a double-sided module the authors of the study needed to find the optimal thickness of the perovskite layer, which had to be thick enough to absorb high-energy photons and thin enough to pass low-energy photons. They also needed to identify the optimal thickness of the back electrode (electrical conductor), which had to be thick enough to minimise resistive losses and thin enough to reduce contact resistance.
By using optical and electrical modeling, the authors concluded that the optimal thickness of the perovskite layer is about 850 nanometres, which is more than 80 times thinner than a human hair. At these parameters, the front layer has an efficiency of 23% and the efficiency of the reverse layer reaches 91% or 93% of that value. At the same time, the output power of the perovskite is affected by the albedo (reflectivity) of the surface under the solar cell. The module’s specific double-sided power reached 28.5 microwatts (µW) per square centimeter with an albedo of 0.3 and 30.1 µW with an albedo of 0.5.
This study could facilitate the commercialisation of double-sided perovskite cells, which is beneficial when both sides of the solar module have an almost identical efficiency. It will also expand the list of advantages offered by perovskites, whose light absorption intensity is so high they can generate electricity not only from the sun, but also from artificial sources such as fluorescent and LED lamps.
