21. C in a band diagram of GaAs / AlGaAs heterojunction -based high-electron-mobility transistor. 22. Two different structures of heterojunctions, a ) phase separated bi-layer and b ) bulk heterojunction . 23. At such a large thickness, only a small fraction of the excitons can reach the heterojunction interface. 24. He applied it to novel low noise quantum well avalanche photodiodes, heterojunction transistors, memory devices and lasers. 25. Fullerenes such as C 60 and its derivatives are used as electron acceptor materials in bulk heterojunction photovoltaic cells. 26. A graphene / n-type silicon heterojunction has been demonstrated to exhibit strong rectifying behavior and high photoresponsivity. 27. These methods are exploited in the design of heterojunction bipolar transistors ( HBTs ), laser diodes and solar cells. 28. More recent developments in OLED architecture improves quantum efficiency ( up to 19 % ) by using a graded heterojunction . 29. The structure of these two layers is the same : it is a heterojunction which catches electrons ( holes ). 30. Fullerenes such as PC 71 BM are often the electron acceptor materials found in high performing bulk heterojunction solar cells.
