Two-dimensional　p-type/intrinsic/n-type　(p-i-n)　homojunction　opens　up　exciting　opportunities　for　the　advancement　of　next-generation　electronic　and　optoelectronic　devices.　However,　it　is　urgent　to　explore　superior　two-dimensional　materials　for　p-i-n　homojunction　to　enhance　optoelectronic　performance.　Herein,　the　electronic　structures,　optical　properties　of　monolayer　XYN3　(X=V,　Nb,　Ta;　Y=Si,　Ge),　and　the　related　p-i-n　homojunctions　are　constructed　and　investigated　systematically　based　on　the　framework　of　density　function　theory　and　non-equilibrium　Green＇s　function　calculations.　The　electronic　structures　and　optical　absorption　of　these　stable　monolayers　reveal　that　they　show　semiconductor　characteristic　with　indirect　bandgaps　of　1.23　similar　to　2.13　eV,　which　possess　strong　absorption　of　visible　light.　The　simulations　of　the　p-i-n　homojunctions　based　on　these　monolayers　highlight　that　VSiN3　and　TaSiN3-based　p-i-n　junctions　possess　maximum　photocurrent　densities　of　21.43　and　18.48　A/m(2),　respectively.　Moreover,　the　photoresponses　of　VSiN3　and　TaSiN3-based　p-i-n　junctions　can　reach　up　to　0.61　and　0.55　A/W,　respectively,　demonstrating　that　VSiN3　and　TaSiN3-based　p-i-n　junctions　could　be　the　ideal　candidates　for　optoelectronic　devices.　Our　work　is　expected　to　pave　the　way　for　the　realization　of　2D　p-i-n　homojunction　optoelectronic　devices.