The big news from Sanyo is that they’ve made a silicon PV cell with a record photoconversion efficiency of 22% (in the laboratory only, not in general manufacture for the folks buying modules for their rooftops). Granted, the previous record was 21.8%, but hey, its progress! Most commercially available single crystal silicon solar cells operate at 18-20% photoconversion efficiency, and the practical limit on efficiency for a first generation PV device is near 28%.^1^

The device is their HIT solar cell, which stands for Heterojunction with Intrinsic Thin layer. Basically, this is a monolithic single crystal silicon cell that has been extensively modified on both external surfaces with texturization and heterojuntions^2^ of amorphous silicon thin films. You can see a general schematic of the design at SolarBuzz.

1. Just to be clear, there are multiple junction solar cells on the market that can achieve photoconversion efficiencies above those of First Generation PV (e.g. triple junction GaAs/GaInP/Ge cells). You won’t be purchasing these for your homes any time soon. These cells are prohibitively expensive for the average consumer: $75,000/m^2^, as opposed to $100/m^2^ for silicon solar cells. They are specifically important to energy in space (as in satellites and Mars rovers). This is because long-term energy delivery is at a premium for space technologies. Governments and large industries have the buying power to launch equipment into space, and hence the finances to purchase the best solar energy delivery systems.
2. A heterojunction occurs when one makes an interface of dissimilar materials, with the goal of electron transfer across the interface (or junction). Amorphous silicon is dissimilar to crystalline silicon, in this case (even though they are composed of the same chemistry).