The main problems of conventional multi-quantum well infrared photodetectors (QWIPs) were discussed. In order to overcome the limitations of the conventional QWIPs, such as small photocurrent, high dark current and low response speed, novel QWIPs in which photocurrent increases with the number of well were proposed. The novel structure with several wells were calculated and analyzed in detail, and successfully fabricated. The dark current lower than conventional QWIPs by about one order of magnitude was obtained, well in agreement with theoretical value. I-V characteristics of the novel QWIPs with six wells has been presented, and six related negative differential resistance regions were observed at positive bias. The absorption photocurrents of the novel QWIPs at 77 K were found to increase with well numbers, confirming the mechanism of the new structure. Furthermore, the transportation of the optoelectronic and some other problems of the QWIPs were discussed. (C) 2002 Elsevier Science B.V. All rights reserved.