Carbon nanotube (CNT)-silicon (Si) heterojunctions show exceptional electrical behavior and hence are promising for electronic and optoelectronic applications. In particular, single wall CNTs (SWCNTs)-Si heterojunctions have been widely studied for these applications. Since multiwall CNTs (MWCNTs) have higher electrical conductivity than SWCNTs, engineering the properties of MWCNTs so as to tailor their electrical properties suitable for heterojunctions can boost the performance of CNT-based electronic and optoelectronic devices. Here the development of MWCNT-Si heterostructures is reported, following surface functionalization and silanization to tailor their structure and properties, at room temperature via solution processing. The developed Al/n-Si/MWCNT/Al heterojunction devices show a low turn-on voltage (approximate to 1-3 V) and high current (approximate to 0.8 mA at 10 V) exceeding the previous high temperature processed CNT-based heterojunctions as well as room temperature grown additional amorphous carbon-Si heterojunctions. The carrier transport mechanism within a carrier-selective contact, multijunction, multiresistance framework, with device current-voltage behavior dictated by transport across the heterojunction and quantum tunneling is discussed. This work opens new direction to design improved devices for future development of large area solution processable CNT based electronics.